This disclosure relates to gas turbine engines, and more particularly to the provision of cooling air for internal components of gas turbine engines.
Gas turbine engines, such as those used to power modern commercial and military aircraft, generally include a compressor section to pressurize an airflow, a combustor section for burning hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases. The airflow flows along a gas path through the gas turbine engine.
Operating temperatures in the turbine section and high pressure compressor portion of the gas turbine engine often exceed the maximum useful temperature of materials used in the components in those portions of the gas turbine engine, so cooling is provided to many of these components via a flow of lower temperature cooling air drawn from other portions of the gas turbine engine. Typical gas turbine engines use engine bypass air (fan bypass) in an air-to-air heat exchanger to lower the temperature of cooling air supplied to the high pressure compressor and the turbine section. Although this method does cool the cooling air sufficiently for current engine configurations there is an upper limit to the amount of cooling available. Further, air-to-air heat exchangers used to cool the cooling air increase weight and packaging volume and are relatively inefficient in cooling air, as the heat that is removed from the cooling air is lost to the cycle.